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Carbohydrates

Carbohydrates. The Chemist’s View of Carbohydrates. Carbohydrates are made of carbon, hydrogen and oxygen atoms. These atoms form chemical bonds that follow the laws of nature. Types of CARBOHYDRATE. Simple Monosaccharide's Glucose Fructose Galactose Disaccharides (Monosac + Glucose)

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Carbohydrates

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  1. Carbohydrates

  2. The Chemist’s View of Carbohydrates • Carbohydrates are made of carbon, hydrogen and oxygen atoms. • These atoms form chemical bonds that follow the laws of nature.

  3. Types of CARBOHYDRATE • Simple • Monosaccharide's • Glucose • Fructose • Galactose • Disaccharides (Monosac + Glucose) • Maltose • Sucrose (Table sugar) • Lactose (Milk sugar)

  4. The Simple Carbohydrates • Monosaccharrides are single sugars • Glucose serves as the essential energy source, and is commonly known as blood sugar or dextrose. • Fructose is the sweetest, occurs naturally in honey and fruits, and is added to many foods in the form of high-fructose corn syrup. • Galactose rarely occurs naturally as a single sugar.

  5. The Simple Carbohydrates • Disaccharides are pairs of monosaccharides, one of which is always glucose • Maltose = glucose + glucose • Sucrose = glucose + fructose • Lactose = glucose + galactose

  6. The Simple Carbohydrates Disaccharides • Maltose = two glucose units. It is produced during the germination of seeds and fermentation. • Sucrose is refined from sugarcane and sugar beets, tastes sweet, and is readily available. Called table sugar • Lactose is found in milk and milk products. Called milk sugar

  7. Your fired, Jack. Your lab results just came back, and you tested positive for Coke

  8. The Complex Carbohydrates • Few (oligosaccharides) or many (polysaccharides) glucose units bound/linked together in straight or branched chains.

  9. Types of CARBOHYDRATE • Complex = Polysaccharides • Starch • Fiber • Glycogen

  10. The Complex Carbohydrates • Starches • Storage form of glucose in plants • Found in grains, tubers, and legumes • Glycogen • Storage form of glucose in the body • Provides a rapid release of energy when needed

  11. Glycogen Starch (amylopectin) Starch (amylose) A glycogen molecule contains hundreds of glucose units in highly branched chains. Each new glycogen molecule needs a special protein for the attachment of the first glucose (shown here in red). A starch molecule contains hundreds of glucose molecules in either occasionally branched chains (amylopectin) or unbranched chains (amylose). Stepped Art Fig. 4-8, p. 106

  12. The Complex Carbohydrates • Dietary fibers provide structure in plants, are very diverse, and cannot be broken down by human enzymes. • Soluble fibers are viscous and can be digested by intestinal bacteria (this property is also known as fermentability). These fibers are found in fruits and vegetables, oats, barley, legumes. • Insoluble fibers are nonviscous and are not digested by intestinal bacteria. These fibers are found in whole grains and vegetables.

  13. Carbohydrates-DietaryGuidelines • Choose fiber-rich fruits, vegetables, and whole grains often • Choose and prepare foods and beverages with little added sugars or caloric sweeteners, such as amounts by the USDA Food Guide and DASH Eating Plan • Reduce incidence of dental caries by practicing good oral hygiene and consuming sugar and starch-containing foods and beverages less frequently

  14. Digestion and Absorption of Carbohydrates • Carbohydrate Digestion • In the mouth, the salivary enzyme amylase begins to hydrolyze starch into short polysaccharides and maltose. • In the stomach, acid continues to hydrolyze starch while fiber delays gastric emptying and provides a feeling of fullness (satiety).

  15. Digestion and Absorption of Carbohydrates • Carbohydrate Digestion • In the small intestine, pancreatic amylase among other enzymes (maltase, sucrase, and lactase) hydrolyzes starches to disaccharides and ultimately monosaccharides. • In the large intestine, fibers remain and attract water, soften stools and ferment.

  16. Digestion and Absorption of Carbohydrates • Carbohydrate Absorption • Primarily takes place in the small intestine • Glucose and galactose are absorbed by active transport. • Fructose is absorbed by facilitated diffusion.

  17. Digestion and Absorption of Carbohydrates • Lactose Intolerance • Symptoms include bloating, abdominal discomfort, and diarrhea. • Causes include lactase deficiency due to a natural decrease that occurs with aging or damaged intestinal villi. • Prevalence • Lowest in Scandinavians and northern Europeans • Highest in Southeast Asians and native North Americans

  18. Digestion and Absorption of Carbohydrates • Lactose Intolerance - Dietary Changes • Increase consumption of milk products gradually. • Mix dairy with other foods. • Spread dairy intake throughout the day. • Use of acidophilus milk, yogurt, and kefir (fermented products) • Use of enzymes • Individualization of diets • Must be careful that vitamin and mineral deficiencies do not develop

  19. Glucose in the Body • The Constancy of Blood Glucose • Maintaining Glucose Homeostasis • Low blood glucose may cause dizziness and weakness. • High blood glucose may cause fatigue. • Extreme fluctuations can be fatal.

  20. Glucose in the Body • A Preview of Carbohydrate Metabolism • The body stores glucose as glycogen in liver and muscle cells. • The body uses glucose for energy if glycogen stores are available. • If glycogen stores are depleted, the body makes glucose from protein. • Gluconeogenesis converting protein to glucose. • Protein-sparing action is having adequate carbohydrate in the diet to prevent the breakdown of protein for energy.

  21. Blood Glucose Regulation High Blood Sugar Dietary CHO • Muscles • Used as fuel • To glycogen Insulin Pancreas Glucagon Liver Liver • Used as fuel • To Glycogen • To Fat Low Blood Sugar • Glycogenolysis • Gluconeogenesis

  22. Glucose in the Body • A Preview of Carbohydrate Metabolism • Making ketone bodies from fat fragments • The accumulation of ketone bodies in the blood is called ketosis. • Ketosis upsets the acid-base balance in the body. • The body can use glucose to make body fat when carbohydrates are consumed excessively.

  23. Glucose in the Body • The Constancy of Blood Glucose • The Regulating Hormones • Insulin moves glucose into the cells and helps to lower blood sugar levels. • Glucagon brings glucose out of liver storage and raises blood sugar levels. • Epinephrine acts quickly to bring glucose out of liver storage during times of stress and stimulates gluconeogenesis.

  24. Glucose in the Body • The Constancy of Blood Glucose • Balance glucose within the normal range by eating balanced meals regularly with adequate complex carbohydrates. • Blood glucose can fall outside the normal range with hypoglycemia or HYPERGLYCEMIA (diabetes).

  25. Glucose in the Body • The Constancy of Blood Glucose • Diabetes • Type 1 diabetes is the less common type with no insulin produced by the body. • Type 2 diabetes is the more common type where fat cells resist insulin. • Prediabetes is blood glucose that is higher than normal but below the diagnosis of diabetes. • Hypoglycemia is low blood glucose and can often be controlled by dietary changes.

  26. Glucose in the Body • The Constancy of Blood Glucose • Glycemic response is how quickly the blood glucose rises and elicits an insulin response. • Glycemic index classifies foods according to their potential for raising blood glucose. • Glycemic load refers to a food’s glycemic index and the amount of carbohydrate the food contains. The benefit of the glycemic index is controversial.

  27. Glycemic Index • is a ranking system for carbohydrates based on their immediate effect on blood glucose levels. It compares carbohydrates gram for gram in individual foods, providing a numerical, evidence-based index of postprandial (post-meal) glycemia.

  28. The effect on blood glucose from a high versus low glycemic index carbohydrate.

  29. Glycemic Index of selected Foods

  30. Glycemic Load • The glycemic load (GL) is a ranking system for carbohydrate content in food portions based on their glycemic index (GI) and the portion size. • The usefulness of glycemic load is based on the idea that a high glycemic index food consumed in small quantities would give the same effect as larger quantities of a low glycemic index food on blood sugar

  31. Health Effects and Recommended Intakes of Sugars • Sugar poses no major health problem except dental caries. • Excessive intakes may displace nutrients and contribute to obesity. • Consuming foods with added sugars should be limited. • Naturally occurring sugars from fruits, vegetables and milk are acceptable sources.

  32. Health Effects and Recommended Intakes of Sugars • Health Effects of Sugars • Foods with added sugars have sugars listed as a first ingredient. • Nutrient deficiencies may develop from the intake of empty kcalories. • Just because a substance is natural does not mean it is nutritious. (Example: honey) • Dental caries may be caused by bacteria residing in dental plaque and the length of time sugars have contact with the teeth.

  33. Health Effects and Recommended Intakes of Sugars • Controversies Surrounding Sugars • Excessive sugar intake can contribute to the development of body fat. • Sugar may be able to alter blood lipid levels and contribute to heart disease • There is no scientific evidence that sugar causes misbehavior in children and criminal behavior in adults. • There is a theory that sugar increases serotonin levels, which can lead to cravings and addictions.

  34. Health Effects and Recommended Intakes of Sugars • Recommended Intakes of Sugars • The USDA Food Guide states that added sugars can be included in the diet as part of discretionary kcalories. • Dietary Guidelines state to limit intake of foods and beverages that are high in added sugars. • DRI suggest added sugars should contribute no more than 25% of a day’s total energy intake.

  35. Health Effects and Recommended Intakes of Starch and Fibers • Health Effects of Starch and Fibers • May be some protection from heart disease and stroke • Soluble fibers bind with bile and thereby lower blood cholesterol levels. • Fiber may also displace fat in the diet. • Reduce the risk of type 2 diabetes by decreasing glucose absorption • Enhance the health of the GI tract which can then block the absorption of unwanted particles • May protect against colon cancer by removing potential cancer-causing agents from the body

  36. Health Effects and Recommended Intakes of Starch and Fibers • Health Effects of Starch and Fibers • Promote weight control because complex carbohydrates provide less fat and added sugar. • Harmful effects of excessive fiber intake • Displaces energy and nutrient-dense foods • Abdominal discomfort and distention • May interfere with nutrient absorption

  37. Recommended Intakes of Starch and Fibers • RDA for carbohydrate is 50-100 g per day, or 45-65% of energy intake. • Daily Value is 300 grams per day. • Dietary Guidelines encourage a variety of whole grains, vegetables, fruits and legumes daily. • Healthy People 2010 recommends six servings of grains and five servings of fruits and vegetables.

  38. Health Effects and Recommended Intakes of Starch and Fibers • Recommended Intakes of Fiber • FDA recommends 25 grams for a 2,000-kcalorie diet. • DRI at 14 g per 1000 kcalorie intake (28 grams for a 2,000 kcalorie diet) • American Dietetic Association recommends 20-35 g per day. • World Health Organization suggests no more than 40 g per day.

  39. Recommended Intakes of Starch and Fibers • From Guidelines to Groceries • Grains – encourage whole grains • Vegetables – starchy and nonstarchy vegetables differ in carbohydrate content • Fruits – vary in water, fiber and sugar content • Milks and Milk Products – contain carbohydrate; cheese is low • Meat and Meat Alternates – meats are low but nuts and legumes have some carbohydrate • Food labels list grams of carbohydrate, fiber and sugar; starch grams can be calculated.

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